Drowning deaths are up in the State of Hawaii. I was there for 8 days, during which 3 people drowned, one at Waipouli, Kauai, near my hotel.
Snorkeling is not strenuous. I’ve done it myself. Strong currents and large waves can kill you, though, and rising sea levels might be contributing to this problem.
The Garden Island newspaper had a very informative article about Kevin Garvey, who almost drowned at Larsen’s Beach. Kevin saw the signs about the dangers, and the 13 recent deaths, but went into the water anyway. He left the shallows and swam into deeper water, when he found he could not get back because the current was against him. Then a large wave hit him and tore off his fins.
His 16-year old son, Taylor, grabbed a Rescue Tube (made available at some beaches), went out, and helped him get back to shore. Without Taylor, Kevin would have died.
Don’t worry about snorkeling, just check out the water conditions. There’s a new campaign in Kauai, “when in doubt, don’t go out.” Mahalo!